  I've liked U2 for a while. I recently acquired some more material, and it reminded me why I like them. I'm currently listening to "Bad", 2 different live versions of it (from "Wide Awake in America" and from "Rattle and Hum"). The first time I listened to this song, I didn't really think much of it, but it really grows on you. Such is the case with everything U2... I didn't really notice/care for them at first, but the more you listen to their work, there's this certain quality and depth of musicality and meaning that starts to surface. Many people get confused about them being a Christian band that sold out their beliefs 20 years ago, but that's not really the case. I'd tell what I know about their whole story concerning that sort of topic, but it will take too long and I have to go study.
What I will say is that although I've never met them and therefore never gotten to know them, after listening to their lyrics and reading myriads of interviews over the years it seems like they're not born again believers. Bono emotionally and intellectually connects to the Bible, but it seems like he really loves the Bible more as a great literary classic. He has stated over the years his belief in it and in the Holy Spirit and whatnot... but never have I seen any Bono or any of them publicy profess that they adhere to the Gospel... ie, that they're sinners in need of salvation, that Christ has redeemed them and called them by name, that they're now on the path of sanctification.
There's a book out by this Irish Presbyterian pastor, called "Walk On" in lieu of a song title from their recent album, that chronicles their "spiritual journey" over they years. I'm interested in reading it, to see if more light can be shed on the subject. Regardless, from a secularly poetic and philosophical point of view, they are deep and they do have very meaningful things to say (namely, Bono since he writes most of the lyrics).
The song "Bad" was written out of the emotional stew of frustration, sympathy, and sorrow over a friend of his at the time that couldn't escape the clutches of heroine addiction. You should listen to it, now that you know that tidbit of info; the song is definitely put into perspective. Off to study. 
